Valves are used in myriad systems and environments to control the flow of a fluid, and may be variously configured to implement this functionality. One exemplary type of valve that is used in some aircraft systems is a butterfly valve. A butterfly valve typically includes a flow body and a butterfly plate. The flow body includes an inner surface that defines a flow channel. The butterfly plate is mounted on a shaft and disposed within the flow channel. An actuation mechanism is coupled to the shaft and, upon supplying a torque to the shaft, causes the butterfly plate to rotate between a closed position and a plurality of open positions. The configuration of the butterfly plate and shaft are such that, at least for low-leakage and relatively high-pressure applications such as bleed air systems, the shaft is arranged to extend through the butterfly plate and across the flow channel at an angle relative to the direction of flow. This allows a suitable seal arrangement to be disposed and maintained between the butterfly plate and the flow body inner surfaces.
For some applications, a butterfly valve may also need to include a manual locking device. The manual locking device, if included, may be coupled to the end of the shaft that is opposite the end to which the actuator is coupled. When the manual locking device is included the shaft should be capable of withstanding the maximum drive torque supplied from the actuator without damaging the shaft. In some butterfly valves, a relatively large diameter shaft may be needed to meet this level of performance. A large diameter shaft may, however, deleteriously impact the flow performance through the valve when it is in its full-open position.
Hence, there is a need for a butterfly valve that can withstand the maximum drive torque supplied from an associated actuator, while at the same time meeting a desired level of flow performance. The present invention addresses at least this need.